Electrical discharge tube



Dec. 27, 1949 E. T. CASELLINI ET AL ELECTRICAL DISCHARGE TUBE Filed Jan.2, 1948 Ezio Thomas Cas ellini Howard B.

INVENTORS Sloan W 13km,

ATTORNEY Patented Dec. 27, 1949 2.492.619 mc'rmcscmscmea runs Ed ThomasCaselllnl, seam, and Howard B.

Sloan, Lynn, Mass., assignors to Sylvanla Electrio Products Inc., Salem,Mass., a corporation of Massachusetts Application January 2, 1948,Serial No. 320

Claims. 1 This invention relates to electric gaseous discharge devicesand particularly to those suitable tions.

Objects of the invention are to produce an inexpensive, compact, emcientdischarge device of improved life in flashing service. Although thedevice is intended principally for producing intense light flashes orelectrical pulses, advantage can be taken of the invention in othertypes of service.

A feature of the invention is a metallic chamber around the cathode andsealed to the glass envelope. Another feature is a cathode of barium ina metallic sleeve, and still another is a cathode conductor and supportwire sealed into an end of said metallic chamber. A further feature is acontrol or starting electrode wrapped around the outside of thedischarge envelope. Other features are a. glass outer envelope, a basefitting over one end thereof, and ventilating holes in said base. Allthese features are not essential to every embodiment of the invention.

Other objects, advantages and features of the invention will be apparentfrom the accompanying specification, in which:

Figure 1 is a cut-away perspective view of a device according to theinvention;

Figure 2 is a similar view of the electrode at one end of the lamp tubeof the device;

Figure 3 is a sectional view of the same electrode before the cathode istreated and the tube sealed; and

Figure 4 is a sectional view of the cathode.

In Figure l, a U-shaped piece of glass tubing I has the lead-in wire 2sealed therethrough at one end to terminate in the anode 3. A metal tube4 is sealed to the other end 5 of the glass tubing I, this tube 4 beingof a metal capable of being sealed to the type of glass used.

The end of tube 4 not sealed to the glass is preferably welded to forman hermetic seal with a piece 6 of tubing, preferably copper or thelike, of good electrical and heat conductivity. Before exhausting thetube l of gases, the copper tube 6 is open at its bottom end I, whichmay be placed in communication with an exhaust system.

A length of copper wire 8 extends into tube 6 along one wall and is bentor crimped over to the opposite part of the tube wall It at a pointremoved from the welded portion II, to form a mechanical or frictionsupport for the wire 8 during the exhaust process. After the exhaustprocedure is completed the tube 6 is pressed together at one point,preferably between the bend I2 and for producing intense discharges ofshort durathe wall I I, to form an hermetic seal in which the wire 8 isfirmly held, and the tube Ii cut of! transversely preferably near themiddle of this crimped portion, after that portion is welded if desired.Solder may be applied to the finished joint.

The cathode I3 may comprise an iron tube I4 sealed at its ends andfilled with barium metal IS. A small hole It in the side of the tubepermits the barium to difiuse gradually to the outside of the cathode asneeded. Some of it may deposit on the inside wall of tube 4 duringoperation.

The anode 3 may be merely a wire, for example an extension ofl'ead-inwire 2, if desired. Its size, particularly its cross-sectionalarea transverse to the tubes longitudinal axis should be proper to givea low anode drop. The tube I may be filled with gas at a pressuresuflicient to operate at the desired voltage. Xenon at 40 mm. of mercurypressure is very effective where an intense light of white color isdesired. Other gases can be used, and may be more suitable where thetube is used for control purposes rather than for illumination. Mercuryvapor may be used, with or without a rare gas, but care should be, takento prevent the vapor pressure becoming sufflcient to explode the tube.If desired, the amount of mercury present in the tube may be kept belowthe quantity necessary to produce too high a pressure when completelyevaporated. When mercury vapor is used, the flash may be made shorterthan usual if the mercury vapor pressure rises quickly enough fromheating by the discharge, to increase the voltage to a value higher thanthat available from the source to which the electrodes are connected.

The tube I may be supported by lead-in wires I1 and 2, attached tochamber 6 and electrode wire 3, respectively, and by the wire l8,wrapped around the outside of glass tube I, to form a control electrode,and in turn connected to lead-in wire I9. Support and lead-in wires I1,2, and I9 extend respectively, into contact pins 20, 2|, 22, afllxedfirmly to the insulating bottom 23 of base 24, whose cylindricalside-wall 25 flts around the tubular portion 25 of glass envelope 21,which may have a rounded top 28. The base 24 and glass envelope 2'!together form an enclosure for the tube I and its supports. Vent holes29 are provided in the bottom portion 23 of bases 24, to allowcirculation of air for cooling the tube I and its chamber 4, 6. The tubeI may get hot enough, in operation, to char paper.

The metal chamber 4, 6 aids in cooling tube I 3 andthegastherein.Insomecases,ltmaybe duirable to put a water Jacket around this electrodefor further cooling.

The electrodes 3 and i 3 may be connected to a source voltage, forexample through pins 20 and 21. This voltage is preferably somewhatbelow the voltage necessary oi. itself to produce a discharge betweenthe electrodes 3 and II, but sumcient to support a discharge once it isstarted by the application of control voltage to electrode II. Theapplication of a comparatively small energy or voltage to electrode l3will thus serve to initiate the discharge. The control voltage willordinarily be applied between cathode l3 and the electrode It.

In one embodiment of our invention, we used a glass tube of .190 inchoutside diameter and 0.11 inch inside diameter, bent into a U or .ishape as in Figure 1, and having a length of about 1% inches alon thecurve. The tube I of metal scalable to glass was of 0.125 inch diameterand A inch long, while the'copper tubing 0 was of 0.1 inch diameter andinch long in the finished tube. The anode 3 was 0.004 inch in diameterand extended about inch into the gas inside the tube. With a filling of40 mm. of xenon this tube operated in a range of 300 to 700 volts acrossthe electrodes I 3 and 3, being triggered oil by a voltage of about 2500to the control electrode it. The tube may be triggered oil in a singleflash, or in a succession oi flashes, for example, at a repetitive rateof 500 per second. The peak currents in the tube may be extremely high,with the average power being only about 5 watts.

For the usual hard glass such as Coming 7052, a potassium bariumborosilicate glass, with a coeiilcient of expansion of about 5 10, themetal tube 4 sealed thereto may be of Kovar," an alloy of 17% cobalt,29% nickel, 0.3% manganese and the balance iron. A softer glass will notpermit as great an instantaneous power, but if used would require anappropriate metal for sealing. The more transparent the glass is to theentire spectrum produced by the gas the cooler the lass will run.

Ii desired, the tube can of course be operated without using the controlelectrode It, by using a high enough voltage across the other electrodes3 and I3 and an appropriate ballast. For flashing operation the tube maybe operated on the discharge of a condenser, as is customary with flashtubes.

The foregoing specific examples are merely by way of explanation and notof limitation. The word glass is used in a broad sense, to include allrefractory light-transmitting materials; in the event the tube is usedas a control tube, the material need not necessarily belight-transmitting.

The tube can be made without the cathode II, and operated as a coldcathode" tube, in which case the voltage required will be much higherand the tube less suitable for a condenser discharge. This drop may besomewhat reduced in 4 thiscasebyeoatingtheinteriorotthchoilow tube 4with electronemissive material.

The tube 4 will act as cathode din-in; operation and as exhaust tubeduring manuiacture.

What we claim is:

1. An electric gaseous discharge lamp comprising a short bent glasstube, a gaseous filling therein, a metal wire anode sealed through andclosing one end of said tube, a metal tube sealed at one of its ends tothe other end of said glass tube, a second metal tube of betterconductivity than the first hermetically attached at one end to the endof said first metal tube extending away from said glass tube, the otherend of said second metal tube being sealed, a conducting wire extendingfrom the sealed end of said second metal tube, a hollow metal tubeattached to said conducting wire and having an opening in its side, anda filling of barium in said hollow metal tube.

2. The combination of claim 1, in which the hollow metal tube having anopening in its side is within the metal tube sealed to the glass tube.

3. The combination of claim 1, a wire control electrode wrapped around aportion of said glass tube, a hollow base, contact pins extendingthrough said base, lead-in wires extendin from said contact pins to theelectrodes to support said tube, and a glass tube closed at one end andfitted into said base at the other end to enclose said tube and itsassociated supports, said base having holes in its end for ventilation.

4. An electric gaseous discharge lamp comprising a short glass tube, agaseous filling therein, a metal anode sealed through and closin one endoi said tube, a metal tube having one of its ends sealed to the otherend of said glass tube, the other end of said metal tube being closed, ahollow metal tube disposed entirely in said firstmentioned metal tubeand connected thereto, and having an opening in its side, and a fillingof barium in said hollow tube.

5. The combination of claim 4, and a conductor wire connectin saidhollow metal tube to said first mentioned tube and having a bendcontacting opposite walls of said first-mentioned metal tube to holdsaid hollow metal tube in place.

mo THOMAS CASEILINT. HOWARD B. SLOAN.

REFERENCES crrEn The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,649,907 Mayer Nov. 22, 19271,994,306 Ewest Mar. 12, 1935 2,094,679 Schouwstra Oct. 5, 19372,107,945 Hull Feb. 8, 1938 2,121,589 Espe June 21, 1938 2,154,542Swanson Apr. 18, 1939 2,237,184 Lemmers Apr. 1, 1941

